I had two fire shrimp. One died yesterday and one died today. I had a small spike in ammonia after I moved my rocks around but that was almost two weeks ago. It went to just over .5 and today it's down to .25. PH, nitrite and nitrate are all good. The fish seem to be doing just fine and both shrimp were very active. My wife thinks it's due to the new Koralia #2 power head but I can't see how that is possible. Anyone have any idea what could have happened? Could the ammonia spike be the cause? The tank has been up for around six months now and was started with sand and water from the old 10 gallon saltwater tank. Thanks.